6.Special Senses Flashcards
describe the eye structure
-2.5 cm diameter sphere
-3 layers
Outline 3 layers of eye
Outermost=Fibrous (sclera and cornea)
Middle=Vascular (choroid, iris and ciliary body)
Innermost=Nervous (retina)
Structure of cornea
-outermost transparent layer
-convex shape
Function of cornea
Refract/ focus light onto the retina
Sclera structure
white outer layer of eye
Function of Sclera
fibrous layer that helps maintain integrity and shape of the eye
Structure of choroid
-lines posterior portion of inner sclera
-rich in blood vessels
Function of choroid
-supplies nutrients to the retina
-light that stimulate photoreceptors in the retina is then absorbed by the choroid
Structure of pupil
Opening in the iris
Function of pupil
-allows light to pass through eye
-Dilate and constrict depending on light levels
Pupil in different light levels
Pupils dilate in low light and constrict in bright light hence changing the amount of light that enters the eye
Structure of iris
smooth muscle ring that is coloured part of eye
Function of iris
-regulates amount of light that enters the eye by controlling the pupil
-can be thin or wide
Iris in different light levels
low light means thin iris
high light means wide iris
How to test pupil function
using a pen light to see dilation and constriction
Structure of ciliary body
-a continuation of choroid
-made of smooth muscle fibres and secretory epithelial cells
Function of ciliary body
-controls shape of lens
-produces aqueous humours that provides nutrients for AVASCULAR structures
Lens structure
biconvex and highly elastic
Function of lens
-adjust the focus of the eye
-refracts and bends light rays
-allows for clear vision
Structure of retina
-inside surface of eyeball that houses photoreceptors
Function of retina
-receives light signals and converts these into neural signals for processing and interpretation
-Contain photoreceptors (rods and cones)
Function of rods
responsible for motion/ black and white vision/ located in periphery of retina
Function of cones
responsible for central vision /colour vision
How many rods and cones
91m rods and 4.5m cones
Structure of optic nerve
-cranial nerve
-originates in retina
Function of optic nerve
-transmits neural messages from retina to the primary visual cortex in the occipital lobe
what type of energy is light
electromagnetic
Function of eyebrows
-protect eyes from dust, foreign material, and sweat by stopping them from entering eye (hairs-link to integumentary)
Function of eyelids
-protect eyes from injury and spread moisture (tears) preventing drying of the eyes (skin-link to integumentary)
Function of eyelashes
-Protect eye from injury and spread moisture (hair-link to integumentary)
Function of lacrimal glands
-provide conjunctiva with oxygen, nutrients and drains wastes
-create tears which contain enzymes which prevent disease from bacterial microbes (link to immune)
-provide secreting fluid that lubricates eyes
Function of conjunctiva
produce mucus and tears
-protects and lubricates eye
location of conjunctiva
lines the inside of eyelids and covers sclera
order of light through eye
cornea, pupil, iris, lens , vitreous humour, retina, optic nerve, occipital lobe
What is the ear
organ of sound and equilibrium
Function of ear
-detect sound waves and convert to nerve signals
-detect changes in position
define a sound wave
when a object vibrates it causes a movement in surrounding air molecules
identify outer ear structure
pinna / auricle
auditory canal
Function of outer ear
collect sound waves
Describe pinna
external, visible part of ear
Function of pinna
shaped to funnel/concentrate/collect sound waves into auditory Canal
Function of auditory/ ear canal
transmit sound waves from pinna to eardrum
Identify middle ear structures
-tympanic membrane (eardrum)
ossicles =malleus, incus, stapes
Function of middle ear
transmit sound waves
Function of ear drum / tympanic membrane
-transmits sound waves to middear via vibrations
-protect middle ear from bacteria and foreign particles
Identify 3 ossicles
malleus -hammer
incus -anvil
stapes-stirrup
pinna =
auricle
ear drum =
tympanic membrane
Function of ossicles
-transmits vibrations/sound waves from outer ear to cochlea
-amplifies sound waves
Identify structures of inner ear
cochlea and vestibular system
Function of inner ear
process sound waves & detect changes in body position
Function of cochlea
transforms sound waves into neural signals
Identify structures of vestibular system
semicircular canals
vestibule
vestibular nerve
which cranial nerve is the optic nerve
2nd
Function of vestibular system
-detects changes in body positions then sends information to brain to maintain equilibrium and balance
Describe the Eustachian tube
connects middle ear to nasopharynx
Function of Eustachian tube
maintains pressure & drains middle ear
Function of vestibular nerve
transmits messages from vestibule to brain about balance and equilibrium
Cochlear nerve function
transmits messages from cochlea to brain to interpret sound
Outline process of hearing
-sound wave generated in environment
-pinna/auricle collects and directs sound waves to auditory canal
-sound waves travel through auditory canal to ear drum
-ear drum vibrates
-vibration transmitted through ossicles which amplify sound waves (mallets, incus, stapes)
-vibrations pass through fluid in cochlea
-hair cells (stereocillia) activated and a nerve impulse is generated
-signals transmitted to brain via cochlea nerve
What fluids detects equilibrium changes
fluids in the semicircular canals and endolymph in the vestibular system detect changes in balance and head position and trigger stereocillia
what receptors detect tastants and odourants
chemoreceptors
describe how we smell
-air enters nasal cavity
-air is warmed, moistened and filtered
-olfactory receptors lining the roof of the nasal cavity detect odourants as they dissolve into muscus membrane
-sensory messages sent to brain via olfactory nerve
what cranial nerve is olfactory nerve
1st
Purpose of tasting
survival/evolutionary purpose
eg bitter taste is associated with poisonous foods and umami is linked to protein
Describe the process of tasting
-food enters mouth
-chemicals from food are dissolved in saliva
-taste receptors on tongue and in mouth detect tastants
-sensory messages sent to brain via facial nerve, glossopharyngeal nerve and vagus nerve
identify the taste. sensations/ flavours
umami
sour
sweet
bitter
salty
brain area for taste
gustatory cortex
brain area for smell
frontal lobe (understanding), components of limbic system eg hypothalamus, amygdala (emotional link)
how does the lens change shape
it gets flatter to look in the distance and bulges for nearby objects
avascular structures of eye
lens, cornea and sclera